the bare PCBs are $75 a pair including shipping

here's a review from one of our many customers . . .

Roy,

This is a great-sounding circuit. 
With your circuit, one of the first things I noticed was that different recordings are clearly different, 
indicating to me that the amplifier is neutral, rather than colored. I was surprised by dynamics in music 
that I hadn't noticed before, especially in classical music. 
This circuit seems able to render complex passages and dynamic variations that made the original circuit 
sound sluggish. I am a trained classical pianist, and I also play Hammond Organ, other vintage keyboards, 
and trumpet, so I know what instruments sound like in real space. The original Dyna circuit made acoustic 
guitar sound "good," but also a bit unnatural--as if the player were playing an acoustic guitar that was 
twenty feet wide. With your circuit, it sounds like someone playing an acoustic guitar right in front of me.

Your circuit is especially wonderful for the MkIII, which I've never thought was a very good-sounding amp 
to begin with. It always seemed kind of grainy/grungy even with upgraded parts. 
The new circuit cleans up the highs and gives the midrange both clarity and natural richness.

I did do a little tube-rolling last night. I swapped some Telefunken ECC81s in place of the Mullards. 
It's hard to say which I like best. The Mullards seem more dynamic, the Telefunkens, a bit smoother.

My brother, for whom I built these, was wowed by them. He says he's going to have to get some speakers 
that will do them justice. I'm playing them into a pair of KEF 104/2s that I think are one of the best speakers 
for tube amps. This new MkIII is very well matched to them and drives them with apparent effortlessness.

Best,
David A.